1. Field of the Invention
The present invention relates to a tape carrier package (TCP) which is a thin semiconductor device, a fabrication method thereof, and a tape carrier.
2. Description of the Related Art
A conventional IC packaging is used for protecting an IC body from external substances and mounting on a circuit board. In recent years, because IC products have an even wider range of applications, and material, size and configuration of packages have become diversified, and as the demand to mount a larger number of pins at an even higher density has increased, the demand to add higher values to the package itself has increased even more.
One such package configuration is a TOP (tape carrier package). A tape carrier herein is a semiconductor device fabricated in the following manner. A device hole is first formed in a flexible base tape, leads (wiring patterns) are formed by, for example, photolithography, and then a solder resist is formed to protect the leads. The TCP is a package in which semiconductor elements are mounted on the tape carrier and sealed by, for example, a resin. A package in which semiconductor element(s) are mounted on a tape carrier but are not sealed by a molding is referred to as a structure.
In a conventional tape carrier, on a photographic film-like base tape made of, for example, polyimide, device holes are formed along the longitudinal direction of the base tape. Many sprocket holes are provided in the vicinity of and along the both width direction edges of the base tape so as to be parallel to the device holes, to facilitate conveyance of the base tape during manufacturing thereof, or the like. A plurality of leads is formed as inner lead portions which protrude toward each device hole. These leads are generally formed of a conductive metal, such as aluminum, copper, or the like. A solder resist is formed on the leads to protect the wiring pattern at a portion of the leads that are on the base tape. The entire surface of each of the leads is plated with Sn (tin), Au (gold), solder, or the like for protection and for bonding the leads.
To mount semiconductor elements on the tape carrier, the semiconductor elements are bonded to the inner lead portions by, for example, eutectic reaction or thermo-compression. Then, a mold is formed by a resin, or the like. Finally, the base tape is cut out to form each package. The package is surface mounted on, for example, a printed wiring board by bonding outer lead portions thereof to the printed wiring board.
A conventional TCP is shown in FIGS. 15A and 15B. FIG. 15A is a plan view of the conventional TCP and FIG. 15B is a sectional view of the conventional TCP taken along line C–C′ of FIG. 15A. A base film 101 is made of, for example, polyimide. Sprocket holes 102 are formed on the base film 101 for conveyance of the base film 101. A semiconductor element 110 includes protruding electrodes 111 which are connected to terminals 103 via inner lead portions 105. The terminals 103 are connected to external circuits. The inner lead portions 105 and the terminals 103 are made of copper, formed by etching and plated with Sn, Au, or solder. The terminals 103 are wider than the inner lead portions. 105. A solder resist 106 is formed on the inner lead portions 105 to protect the copper-made pattern except the terminals 103. A sealing resin 112 is provided to cover and protect the semiconductor element 110 and the inner lead portions 105.
Another conventional TCP is shown in FIGS. 16A and 16B, which is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-21703. FIG. 16A is a plan view of an IC package and FIG. 16B is a sectional view taken along line C–C′ of FIG. 16A. This TCP is fabricated in the following manner. Device holes 104 are formed on a tape base 102. Leads 108 are provided on the tape base 102 at the periphery of the device hole 104. Several semiconductor chips 106 are stacked in the device hole 104. Tips of the leads 108 are formed as inner lead portions 108a, which are connected to bumps 110 disposed on the semiconductor chips 106. Then, the semiconductor chips 106 and the device hole 14 are sealed by, for example, a sealing resin 112. This conventional structure has drawbacks in that, because the semiconductor chips 106 are stacked with chip surfaces on which leads 108 are to be bonded facing each other, it is necessary to overturn the package during bonding of the leads 108. Further, because only the leads extending in opposed two directions are connected to each semiconductor chip 106, there are limits to increasing packaging density of semiconductor chips.
For several years, an IC package, known as a BGA (i.e., ball grid array) package which can be mounted at a high density on a printed wiring board, has been developed. In the BGA package, metal balls for connecting to external circuits are disposed in a grid-like pattern at the bottom of the IC package. In this configuration, because terminals for external connection are disposed in a two-dimensional plane, the number of pins can be increased without changing the dimensions of the package very much.
FIGS. 17A and 17B illustrate a BGA structure disclosed in JP-A No. 8-148526, which uses a tape carrier. FIG. 17A is a sectional elevation view, and FIG. 17B is a bottom view, of a BGA type IC package. The BGA semiconductor device has excellent moisture resistance property, and can be fabricated at a low cost, and can be produced in large quantities. In the BGA semiconductor device, a device hole 102a is formed in the center of a flexible resin substrate made of, for example, polyimide film. Leads 103 formed of a copper foil are provided at a surface of the substrate, and the substrate is used as a TCP substrate. Tips of the leads 103 are formed as inner lead portions 103a, which are connected to electrodes 101a of a semiconductor chip 101. Each lead 103 is connected to a corresponding bump 105, such as a solder ball disposed at the bottom surface of the package.
In such conventional tape carriers, only one semiconductor element can be mounted on a single tape carrier, and it is difficult to mount several semiconductor elements, particularly semiconductor elements having different sizes, on a single tape carrier at a high density to improve functions of the semiconductor package.
In the package configuration which employs a combination of the tape carrier and the BGA, a larger number of external terminals may be extended from a package of the same size as those of conventional ones. However, it is very difficult to improve functions of the package itself by densely mounting several semiconductor elements on a single tape carrier.